1. Field of the Invention
The present invention is directed to a miniature transfer relay having normally-closed and normally-open contacts.
2. Description of the Prior Art
In a prior miniature transfer relay, it is common to mount a contact assembly on a relay base, for example, as disclosed in U.S. Pat. No. 4,933,654. The contact assembly includes a set of normally-open (NO) and normally-closed (NC) contacts, and associated contacts carried on a movable spring which are all disposed to project on the base. With this mounting structure, the relay is required to have an increased height for accommodating the contact assembly, which is a hindrance to miniaturization of the relay. In order to reduce the height dimension of the contact assembly, another prior transfer relay has been proposed to mold the NO and NC contacts in the surface of the base, while disposing only the movable spring to project on the base, for example, as disclosed in the European Patent Publication EP 0 100 165 B1. However, the transfer relay of this type requires the movable spring to have a rather complicated configuration having first and second movable contacts corresponding respectively to the NO and NC fixed contacts. In order to obtain transfer operation, the movable spring is made as an elongated member which is pivotally supported intermediate its longitudinal ends and is provided on the opposed longitudinal ends with the first and second movable contacts in correspondence to the NO and NC fixed contacts. It is this pivot structure that adds the complexity to the configuration of the movable spring and also requires the movable spring to have an increased length, which makes the prior art transfer relay still insufficient for achieving further miniaturization with a simple contact assembly structure.